Problem
After upgrading the Adaptive Security Appliance (ASA) from version 8.2(2) to 8.2(3), the user could not connect with AnyConnect with the Cisco Secure Desktop (CSD) enabled. If CSD is disabled the user could connect without problems. The user gets a certificate error "%ASA-7-725014 SSL lib error. Function: SSL3_READ_BYTES Reason: sslv3 alert certificate unknown".
Resolution
This issue occurs due to the to the Cisco Bug id CSCti73316. Upgrading to AnyConnect VPN Client release 2.5.2001 will resolve this issue. Try disabling CSD if the issue exists after upgrading the AnyConnect client.
Source: https://supportforums.cisco.com/thread/2041559?tstart=0